Precipitation hardened copper alloy



Patented Dec. 17, 1940 UNITED STATES PRECIPITATION HARDENED COPPER ALLOY Richards H. Harrington, Schenectady, N. Y., assignor to General Electric Company, a corporation of New York No Drawing. Application September 12, 1936, Serial No. 100,561

4 Claims.

The present invention relates to precipitation hardened copper alloys and more particularly to a process for improving the properties of copperchromium-beryllium alloys. An alloy of this 5 composition is disclosed in the patent to Dahl 1,847,929 and contains about 0.1% to 1% beryllium, about 0.4% to 6% chromium, with the remainder copper. The alloy disclosed in the patent is age or precipitation hardened by heat- 10 ing it to an elevated temperature, quenching and reheating to an intermediate temperature.

v When precipitation hardened, this alloy is relatively soft and I have found that its properties r may be improved by cold working and also by cold working followedby an additional heat treatment.

If cast rods about 1 inches thick and containing 0.4% chromium, 0.1% beryllium, and about 99.5% copper are precipitation hardened in the usual manner, for example, by heating for about one hour at 900 C., quenching in water, cold swaging to 1 inch diameter and then reheating to 475 C. for an hour the following properties are obtained:

Tensile strength 47,700 lbs/sq. in. Proportional limit 30,000 lbs/sq. in. Elongation 27% Hardness 63 Rockwell B. Electrical conductivity 71% that of copper The structure obtained in the cast rod by the above process is characterized by the presence of the usual slip bands which. are present in substantially all cold worked alloys. Also the room temperature physical properties of the alloy are relatively unafiected by reheating up to about 400 C. and recooling.

I have found that if the 1%, inch rods of the above noted composition are heated for about one hour at a temperature of 900 C., quenched in water, then reheated at 500 C. for one hour, air cooled and then swaged to 1 inch diameter the following properties are obtained:

Tensile strength 49,400 lb./sq. in.

Proportional limit 35,200 lbs/sq. in. Elongation 12% Hardness 70 Rockwell B Electrical conductivity 67% of that of copper Cold working after precipitation hardening,

material. It is understood, of course, that cold working can also be accomplished by rolling, forging, etc.

If the material thus produced is now reheated at about 100 C. for about 1 hours and air 5 cooled, the following properties are obtained:

Tensile strength 50,600 lbs/sq. in. Proportional limit 35,300 lbs/sq. in. Elongation 11% 10 Hardness 73 Rockwell B Electrical conductivity 66.4% of that of copper These properties are relatively unafi'ected by reheating up to about 300 C. and recooling. However, reheating to temperatures about 300 C. 15 results in an increase in electrical conductivity at the expense of lower tensile strength. Reheating to a secondary aging temperature above 400 0. results in properties inferior to those obtained by a single aging followed by cold 20 working.

The specific application of the above alloy obviously will determine which of the above treatments, i.'e. (1) precipitation hardening followed by cold working, or (2) precipitationhardening 25 followed respectively by cold working and reheating should be employed. The first treatment is particularly adapted for the production of material to be used in the manufacture of 6180-,- trical conducting springs while the second proc- 30 ess which is in effect a double aging process with intermediate cold working between the first and second reheat is adapted for use where maximum hardness is of importance as in resistance welding electrodes. 35

What I claim is new and desire to secure by Letters Patent of the United States:

1. The process for improving the properties of precipitation hardened alloys consisting of about 0.1% to 1% beryllium and 0.4% to 6% chromium and the remainder copper, which comprises cold working said precipitation hardened alloy and thereafter aging said alloy.

2. The process for improving the properties of precipitation hardened alloys consisting of about 0.1% .to 1% beryllium and 0.4% to 6% chromium and the remainder copper, which comprises cold working said precipitation hardened alloy and thereafter reheating said alloy at a temperature of about 100 C. and cooling. 50

' 3. The process for improving the properties of a precipitation hardened alloy containing about 0.1% to 1% beryllium, 0.4% to 4% chromium with the remainder copper, which comprises producing a condition of strain in said with the remainder copper, which comprises producing a condition of strain in said precipitation hardened alloy by cold working, and thereafter reheating said alloy at a temperature of about 100 C. for about 1 hours and air cooling from 5 that temperature.

RICHARDS H. HARRINGTON. 

